If you have single pane windows, then yes, replace them! The energy savings will pay for those windows within their lifespan. If your windows are not single pane, replacing them will not help you save much energy.

A quick primer on how to make good window choices

In terms of air tightness, all else being equal, fixed windows (i.e. you can’t open them) are the most airtight, followed by hinged windows, with the worst windows being sliders. For historical reasons or simple preference, you can of course choose sliders without feeling terrible about it since modern windows are good.

When purchasing windows, you’ll likely have the choice of which low-e coating is on them. Low-e (or low emissivity coating) is like an emergency blanket to keep your windows warm.

There are several choices of coatings with different properties. Some allow more of the sun’s heat in and some have a solar blocking coating which is more insulative. If you choose solar-blocking coatings, you’ll get less heat through the window, which also increases its insulative value slightly. For a kitchen, or large windows facing west, this is generally a pretty decent choice.

Some low-e coatings allow more sunlight to enter, and in our heating-dominated climate, will have a better energy rating as a result. You’ll always have argon gas inside new windows (unless you’re buying high end windows, in which case this primer will do little to help).

There are lots of options for windows. Often price is a deciding factor, so I’ll just say that:

Exposed wood on the outside of the window isn’t great for maintenance or durability.

Triple glazed windows should cost about 10% more than double glazed windows, but you’ll gain an inordinate sense of pride, while also avoiding most of the condensation that windows are prone to experience.

Different colours add between 15-25% to the cost, so if you are willing to do that, you should at least do triple-glazed windows. It’s only fair.

More tips on making good window choices

Here are the slides from a presentation I made with additional information on how to choose windows.